JP2012187490A - Method for cleaning nitrite nitrogen - Google Patents
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Abstract
Description
本発明は、亜硝酸性窒素の浄化方法に関する。 The present invention relates to a method for purifying nitrite nitrogen.
貴金属製造・再生業などの各種産業において、高濃度の硝酸性窒素（ＮＯ３ −）や亜硝酸性窒素（ＮＯ２ −）を含む廃液が発生している。現状、このような廃液を処理する方法としては、希釈した上で下水道へ排出する方法が採られている。 In various industries such as precious metal manufacturing / recycling, waste liquids containing high concentrations of nitrate nitrogen (NO 3 − ) and nitrite nitrogen (NO 2 − ) are generated. At present, as a method of treating such waste liquid, a method of diluting and discharging to the sewer is used.
しかし、近年、高濃度の硝酸性窒素や亜硝酸性窒素を含む廃液の排出規制が厳しくなっており、このような廃液中の硝酸性窒素や亜硝酸性窒素を効率的に低濃度化する技術が早急に求められている。 However, in recent years, regulations on the discharge of waste liquids containing high concentrations of nitrate nitrogen and nitrite nitrogen have become stricter, and technologies for efficiently reducing the concentration of nitrate nitrogen and nitrite nitrogen in such waste liquids. Is urgently needed.
水性液中の硝酸性窒素や亜硝酸性窒素を低濃度化する従来の技術として、イオン交換、逆浸透、電気化学透析などを利用した物理化学的脱窒素方法、独立栄養細菌などを用いる生物学的脱窒素方法、電解還元などを利用した電気化学的脱窒素方法、水素ガスを用いた触媒法などが報告されている（例えば、特許文献１、特許文献２など参照）。しかし、これら従来の技術においては、例えば、低濃度化の効率が低いという問題、ラージスケールへの適用が難しいという問題、高濃度の硝酸性窒素や亜硝酸性窒素を含む水性液への適用が難しいという問題、装置コストが大きいという問題、環境負荷が十分に低減されていないという問題、有害な副生成物が発生するという問題などがある。 Conventional techniques for reducing nitrate and nitrite nitrogen concentrations in aqueous solutions include physicochemical denitrification methods using ion exchange, reverse osmosis, and electrochemical dialysis, and biology using autotrophic bacteria. There have been reported an automatic denitrification method, an electrochemical denitrification method using electrolytic reduction, a catalytic method using hydrogen gas, and the like (see, for example, Patent Document 1 and Patent Document 2). However, in these conventional techniques, for example, there are problems such as low efficiency of concentration reduction, difficulty in application to large scale, and application to aqueous liquids containing high concentrations of nitrate nitrogen and nitrite nitrogen. There are problems such as difficulty, large equipment cost, environmental load is not sufficiently reduced, and harmful by-products are generated.
さらに、水性液中の硝酸性窒素や亜硝酸性窒素を低濃度化する技術を、貴金属製造・再生業などの各種産業において排出された廃液中の硝酸性窒素や亜硝酸性窒素の浄化に適用する際には、上記問題の解決に加えて、高い安全性が求められる。 Furthermore, the technology to reduce the concentration of nitrate nitrogen and nitrite nitrogen in aqueous liquids is applied to purification of nitrate nitrogen and nitrite nitrogen in waste liquids discharged in various industries such as precious metal manufacturing and recycling industries. In doing so, in addition to solving the above problems, high safety is required.
本発明の課題は、水性液中の硝酸性窒素や亜硝酸性窒素を高効率で低濃度化する方法を提供することであって、ラージスケールへの適用が可能であり、高濃度の硝酸性窒素や亜硝酸性窒素を含む水性液への適用が可能であり、装置コストを低減でき、環境負荷が十分に低減され、有害な副生成物の発生を抑制でき、安全性の高い、水性液中の硝酸性窒素や亜硝酸性窒素の浄化方法を提供することにある。 An object of the present invention is to provide a method for reducing the concentration of nitrate nitrogen and nitrite nitrogen in an aqueous liquid with high efficiency, which can be applied to a large scale and has a high concentration of nitrate. It can be applied to aqueous liquids containing nitrogen and nitrite nitrogen, can reduce equipment costs, sufficiently reduce environmental impact, suppress the generation of harmful by-products, and is highly safe. It is to provide a purification method for nitrate nitrogen and nitrite nitrogen.
本発明は、亜硝酸性窒素の浄化方法に関する。本発明は、水性液中に含まれる亜硝酸性窒素を浄化する方法であって、光触媒およびアンモニウムイオンの存在下で光触媒反応を行う。 The present invention relates to a method for purifying nitrite nitrogen. The present invention is a method for purifying nitrite nitrogen contained in an aqueous liquid, and performs a photocatalytic reaction in the presence of a photocatalyst and ammonium ions.
好ましい実施形態においては、上記光触媒が酸化物半導体型光触媒である。 In a preferred embodiment, the photocatalyst is an oxide semiconductor photocatalyst.
好ましい実施形態においては、上記光触媒反応中の上記水性液の温度が５０℃以下である。 In a preferred embodiment, the temperature of the aqueous liquid during the photocatalytic reaction is 50 ° C. or lower.
好ましい実施形態においては、上記アンモニウムイオンがアンモニア由来である。 In a preferred embodiment, the ammonium ion is derived from ammonia.
好ましい実施形態においては、上記光触媒反応開始時の上記水性液のｐＨを６〜８に調整する。 In a preferred embodiment, the pH of the aqueous liquid at the start of the photocatalytic reaction is adjusted to 6-8.
好ましい実施形態においては、上記ｐＨの調整のためにアンモニアを用いる。 In a preferred embodiment, ammonia is used to adjust the pH.
好ましい実施形態においては、上記亜硝酸性窒素が、硝酸性窒素に対する光触媒反応によって得られる。 In a preferred embodiment, the nitrite nitrogen is obtained by a photocatalytic reaction on nitrate nitrogen.
好ましい実施形態においては、上記硝酸性窒素に対する光触媒反応が、酸化物半導体型光触媒および貴金属系助触媒の存在下で行われる。 In a preferred embodiment, the photocatalytic reaction with respect to nitrate nitrogen is performed in the presence of an oxide semiconductor type photocatalyst and a noble metal promoter.
好ましい実施形態においては、上記水性液が廃液である。 In a preferred embodiment, the aqueous liquid is a waste liquid.
好ましい実施形態においては、上記廃液が貴金属製造・再生業において排出される廃液である。 In a preferred embodiment, the waste liquid is a waste liquid discharged in a precious metal manufacturing / recycling industry.
本発明の浄化方法によれば、水性液中の硝酸性窒素や亜硝酸性窒素を高効率で低濃度化することができる。本発明の浄化方法は、ラージスケールへの適用が可能であり、高濃度の硝酸性窒素や亜硝酸性窒素を含む水性液への適用が可能であり、装置コストを低減でき、環境負荷が十分に低減され、有害な副生成物の発生を抑制でき、安全性が高い。 According to the purification method of the present invention, nitrate nitrogen and nitrite nitrogen in an aqueous liquid can be reduced with high efficiency. The purification method of the present invention can be applied to a large scale, can be applied to an aqueous liquid containing a high concentration of nitrate nitrogen or nitrite nitrogen, can reduce the cost of the apparatus, and has a sufficient environmental load. Therefore, the generation of harmful by-products can be suppressed and safety is high.
本発明は、亜硝酸性窒素（ＮＯ２ −）の浄化方法に関する。具体的には、本発明は、水性液中に含まれる亜硝酸性窒素を浄化する方法である。 The present invention relates to a method for purifying nitrite nitrogen (NO 2 − ). Specifically, the present invention is a method for purifying nitrite nitrogen contained in an aqueous liquid.
本発明は、水性液中に含まれる亜硝酸性窒素を浄化する方法であるが、水性液中に硝酸性窒素（ＮＯ３ −）が含まれる場合にも適用できる。すなわち、後述するように、水性液中に硝酸性窒素（ＮＯ３ −）が含まれる場合には、該硝酸性窒素を、任意の適切な反応を行うことによって、亜硝酸性窒素に変換すればよい。 The present invention is a method for purifying nitrite nitrogen contained in an aqueous liquid, but can also be applied to cases where nitrate nitrogen (NO 3 − ) is contained in an aqueous liquid. That is, as will be described later, when nitrate nitrogen (NO 3 − ) is contained in the aqueous liquid, the nitrate nitrogen can be converted into nitrite nitrogen by performing any appropriate reaction. Good.
本発明の浄化方法の好ましい実施形態の一つは、下記一般式（２）に示すように、水性液中に含まれる亜硝酸性窒素を浄化する方法であって、光触媒およびアンモニウムイオンの存在下で光触媒反応を行い、窒素に転化する。さらに好ましくは、下記一般式（１）に示すように、上記亜硝酸性窒素が、硝酸性窒素に対する光触媒反応によって得られる。
ＮＯ３ − →〔光触媒反応〕→ ＮＯ２ − ・・・（１）
ＮＯ２ − ＋ ＮＨ４ ＋ →〔光触媒反応〕→ Ｎ２ ・・・（２）
One preferred embodiment of the purification method of the present invention is a method for purifying nitrite nitrogen contained in an aqueous liquid as shown in the following general formula (2), in the presence of a photocatalyst and ammonium ions. To photocatalyze and convert to nitrogen. More preferably, as shown in the following general formula (1), the nitrite nitrogen is obtained by a photocatalytic reaction with respect to nitrate nitrogen.
NO 3 − → [Photocatalytic reaction] → NO 2 − (1)
NO 2 − + NH 4 + → [photocatalytic reaction] → N 2 (2)
本発明の浄化方法を適用できる水性液中の亜硝酸性窒素の濃度としては、低濃度（例えば、１００μｍｏｌ／Ｌ以下）から高濃度（例えば、１０ｍｏｌ／Ｌ以上）に至るまで、任意の適切な濃度を採用し得る。 The concentration of nitrite nitrogen in the aqueous liquid to which the purification method of the present invention can be applied is any appropriate value from low concentration (for example, 100 μmol / L or less) to high concentration (for example, 10 mol / L or more). Concentration can be employed.
本発明の浄化方法は、高濃度（例えば、１０ｍｏｌ／Ｌ以上）の亜硝酸性窒素を含む水性液に適用できるので、貴金属製造・再生業などの各種産業において排出された廃液中の硝酸性窒素や亜硝酸性窒素の浄化に適用できる。 Since the purification method of the present invention can be applied to an aqueous liquid containing a high concentration (for example, 10 mol / L or more) of nitrite nitrogen, nitrate nitrogen in waste liquid discharged in various industries such as precious metal manufacturing / regeneration industries. It can be applied to purify nitrous acid nitrogen.
本発明の浄化方法においては、光触媒およびアンモニウムイオン（ＮＨ４ ＋）の存在下で光触媒反応を行う。 In the purification method of the present invention, the photocatalytic reaction is carried out in the presence of a photocatalyst and ammonium ions (NH 4 + ).
上記光触媒としては、任意の適切な光触媒を採用し得る。このような光触媒としては、好ましくは、酸化物半導体型光触媒である。酸化物半導体型光触媒としては、例えば、ＢｅＯ、ＭｇＯ、ＣａＯ、ＳｒＯ、ＢａＯ、ＣｅＯ２、ＴｈＯ２、ＵＯ３、Ｕ３Ｏ８、ＴｉＯ２、ＺｒＯ２、Ｖ２Ｏ５、Ｙ２Ｏ３、Ｙ２Ｏ２Ｓ、Ｎｂ２Ｏ５、Ｔａ２Ｏ５、ＭｏＯ３、ＷＯ３、ＭｎＯ２、Ｆｅ２Ｏ３、ＭｇＦｅ２Ｏ４、ＮｉＦｅ２Ｏ４、ＺｎＦｅ２Ｏ４、ＺｎＣｏ２Ｏ４、ＺｎＯ、ＣｄＯ、Ａｌ２Ｏ３、ＭｇＡｌ２Ｏ４、ＺｎＡｌ２Ｏ４、Ｔｌ２Ｏ３、Ｉｎ２Ｏ３、ＳｉＯ２、ＳｎＯ２、ＰｂＯ２、ＵＯ２、Ｃｒ２Ｏ３、ＭｇＣｒ２Ｏ４、ＦｅＣｒＯ４、ＣｏＣｒＯ４、ＺｎＣｒ２Ｏ４、ＷＯ２、ＭｎＯ、Ｍｎ３Ｏ４、Ｍｎ２Ｏ３、ＦｅＯ、ＮｉＯ、ＣｏＯ、Ｃｏ３Ｏ４、ＰｄＯ、ＣｕＯ、Ｃｕ２Ｏ、Ａｇ２Ｏ、ＣｏＡｌ２Ｏ４、ＮｉＡｌ２Ｏ４、Ｔｌ２Ｏ、ＧｅＯ、ＰｂＯ、ＴｉＯ、Ｔｉ２Ｏ３、ＶＯ、ＭｏＯ２、ＩｒＯ２、ＲｕＯ２、ＣｄＳ、ＣｄＳｅ、ＣｄＴｅなどが挙げられる。これらの酸化物半導体型光触媒の中でも、触媒活性の高さ、入手のし易さなどの点からは、ＴｉＯ２が好ましい。 Any appropriate photocatalyst can be adopted as the photocatalyst. Such a photocatalyst is preferably an oxide semiconductor type photocatalyst. Examples of the oxide semiconductor type photocatalyst include BeO, MgO, CaO, SrO, BaO, CeO 2 , ThO 2 , UO 3 , U 3 O 8 , TiO 2 , ZrO 2 , V 2 O 5 , Y 2 O 3 , Y 2 O 2 S, Nb 2 O 5, Ta 2 O 5 , MoO 3 , WO 3 , MnO 2 , Fe 2 O 3 , MgFe 2 O 4 , NiFe 2 O 4, ZnFe 2 O 4, ZnCo 2 O 4 , ZnO, CdO, Al 2 O 3 , MgAl 2 O 4 , ZnAl 2 O 4 , Tl 2 O 3 , In 2 O 3 , SiO 2 , SnO 2 , PbO 2 , UO 2 , Cr 2 O 3 , MgCr 2 O 4 , FeCrO 4, CoCrO 4, ZnCr 2 O 4, WO 2, MnO, Mn 3 O 4, Mn 2 O 3, FeO, NiO, CoO, Co 3 O 4, PdO, CuO, Cu Include O, Ag 2 O, CoAl 2 O 4, NiAl 2 O 4, Tl 2 O, GeO, PbO, TiO, Ti 2 O 3, VO, MoO 2, IrO 2, RuO 2, CdS, CdSe, etc. CdTe is It is done. Among these oxide semiconductor photocatalysts, TiO 2 is preferable from the viewpoints of high catalytic activity and availability.
上記光触媒は、１種のみを用いてもよいし、２種以上を併用してもよい。 Only 1 type may be used for the said photocatalyst and it may use 2 or more types together.
上記光触媒には、助触媒が併用されてもよい。このような助触媒としては、例えば、金、白金、パラジウム、銀、銅、ロジウムなど、任意の適切な貴金属系助触媒が挙げられる。助触媒の量としては、任意の適切な量を採用し得る。このような助触媒は、１種のみを用いてもよいし、２種以上を併用してもよい。 A cocatalyst may be used in combination with the photocatalyst. Examples of such promoters include any suitable noble metal promoters such as gold, platinum, palladium, silver, copper, and rhodium. Any appropriate amount can be adopted as the amount of the cocatalyst. Only 1 type may be used for such a co-catalyst and it may use 2 or more types together.
水性液中の光触媒の量としては、光触媒反応が起こり得る量であれば、任意の適切な量を採用し得る。このような光触媒の量としては、水性液全量に対して、好ましくは０．０２〜２０重量％であり、より好ましくは０．２〜２．０重量％である。 As an amount of the photocatalyst in the aqueous liquid, any appropriate amount can be adopted as long as the photocatalytic reaction can occur. The amount of such a photocatalyst is preferably 0.02 to 20% by weight, more preferably 0.2 to 2.0% by weight, based on the total amount of the aqueous liquid.
上記アンモニウムイオンとしては、任意の適切なアンモニウムイオン発生源から供給されるアンモニウムイオンを採用し得る。このようなアンモニウムイオン発生源としては、好ましくは、アンモニア（ＮＨ３）が挙げられる。 As said ammonium ion, the ammonium ion supplied from arbitrary appropriate ammonium ion generation sources can be employ | adopted. Such an ammonium ion generation source is preferably ammonia (NH 3 ).
アンモニウムイオン発生源としてアンモニアが採用される場合、該アンモニアは、例えば、別途入手したアンモニアであってもよいし、任意の適切な工業製品等の製造工程において排出されたアンモニアであってもよい。好ましい実施形態の一つとして、例えば、本発明の浄化方法が貴金属製造・再生業などの各種産業において排出された廃液中の硝酸性窒素や亜硝酸性窒素の浄化に適用される場合、該貴金属製造・再生業などにおける製造工程において排出されたアンモニアを、本発明の浄化方法におけるアンモニウムイオン発生源として用いる形態が挙げられる。 When ammonia is employed as the ammonium ion generation source, the ammonia may be, for example, ammonia obtained separately or ammonia discharged in a manufacturing process of any appropriate industrial product or the like. As one preferred embodiment, for example, when the purification method of the present invention is applied to purification of nitrate nitrogen or nitrite nitrogen in waste liquid discharged in various industries such as precious metal production / regeneration industry, the noble metal The form which uses the ammonia discharged | emitted in the manufacturing process in manufacture / regeneration industry etc. as an ammonium ion generation source in the purification method of this invention is mentioned.
水性液中のアンモニウムイオンの濃度としては、光触媒反応が起こり得る量であれば、任意の適切な量を採用し得る。このようなアンモニウムイオンの濃度としては、水性液全量に対して、好ましくは１００μｍｏｌ／Ｌ〜１０ｍｏｌ／Ｌであり、より好ましくは１ｍｍｏｌ／Ｌ〜５ｍｏｌ／Ｌである。 As the concentration of ammonium ions in the aqueous liquid, any appropriate amount can be adopted as long as the photocatalytic reaction can occur. The concentration of such ammonium ions is preferably 100 μmol / L to 10 mol / L, more preferably 1 mmol / L to 5 mol / L with respect to the total amount of the aqueous liquid.
上記光触媒反応の条件としては、任意の適切な条件を採用し得る。 Arbitrary appropriate conditions can be employ | adopted as conditions for the said photocatalytic reaction.
上記光触媒反応の条件として、例えば、照射光としては、太陽光などの自然光であってもよいし、蛍光灯、ブラックライト、キセノンランプ、水銀ランプ、ハロゲンランプ、ＬＥＤなどの人工光（紫外光など）であってもよい。 As conditions for the photocatalytic reaction, for example, the irradiation light may be natural light such as sunlight, or artificial light (such as ultraviolet light) such as a fluorescent lamp, a black light, a xenon lamp, a mercury lamp, a halogen lamp, or an LED. ).
上記光触媒反応の条件として、例えば、光触媒反応中の上記水性液の温度としては、任意の適切な温度を採用し得る。しかしながら、本発明の浄化方法においては、上記光触媒反応中の上記水性液の温度を常温付近で行うことが可能である。すなわち、本発明の浄化方法においては、上記光触媒反応中の上記水性液の温度が、好ましくは５０℃以下であり、より好ましくは０〜４５℃であり、さらに好ましくは２〜４０℃以下であり、特に好ましくは５〜３０℃である。本発明の浄化方法において、上記光触媒反応中の上記水性液の温度を常温付近で行うことが可能であれば、浄化に費やすエネルギーを低減できるだけでなく、該水性液が有毒な揮発性物質を含む廃液である場合には、該有毒な揮発性物質の揮散を抑制することが可能となり、また、水性液温度上昇による副反応の発生に起因する安全性低下の問題も回避可能となる。 As conditions for the photocatalytic reaction, for example, any appropriate temperature can be adopted as the temperature of the aqueous liquid during the photocatalytic reaction. However, in the purification method of the present invention, it is possible to perform the temperature of the aqueous liquid during the photocatalytic reaction at around room temperature. That is, in the purification method of the present invention, the temperature of the aqueous liquid during the photocatalytic reaction is preferably 50 ° C. or lower, more preferably 0 to 45 ° C., further preferably 2 to 40 ° C. or lower. Especially preferably, it is 5-30 degreeC. In the purification method of the present invention, if the temperature of the aqueous liquid during the photocatalytic reaction can be performed near room temperature, not only can the energy consumed for purification be reduced, but the aqueous liquid contains a toxic volatile substance. In the case of a waste liquid, it is possible to suppress the volatilization of the toxic volatile substance, and it is also possible to avoid the problem of a decrease in safety due to the occurrence of a side reaction due to an increase in aqueous liquid temperature.
従来、亜硝酸性窒素とアンモニウムイオンとは、熱化学反応によって反応して窒素に転化できることは知られているが、その反応を進行させるためには、７０℃以上の熱エネルギーを与えることが必要であり、たとえそのような高い熱エネルギーを与えても、十分な反応は起こらない（５時間後の転化率として２０％程度）。また、亜硝酸性窒素とアンモニウムイオンとを、光化学反応によって反応させて窒素に転化しようとしても、窒素はほとんど発生しない（５時間後の転化率として１０％程度）。 Conventionally, it is known that nitrite nitrogen and ammonium ions can be converted into nitrogen by reaction through a thermochemical reaction, but it is necessary to give thermal energy of 70 ° C. or higher in order to advance the reaction. Even if such high heat energy is applied, sufficient reaction does not occur (the conversion rate after 5 hours is about 20%). Further, even if nitrite nitrogen and ammonium ions are reacted by a photochemical reaction and converted to nitrogen, nitrogen is hardly generated (the conversion rate after 5 hours is about 10%).
本発明の浄化方法においては、光触媒を用いた光触媒反応を、亜硝酸性窒素とアンモニウムイオンとの反応に利用したところ、驚くべきことに、非常に高い転化率で窒素に転化できることが判り、しかも、その光触媒反応中の上記水性液の温度を常温付近で行っても、非常に高い転化率で窒素に転化できることが判った。 In the purification method of the present invention, when the photocatalytic reaction using a photocatalyst is used for the reaction between nitrite nitrogen and ammonium ions, it is surprisingly found that it can be converted to nitrogen at a very high conversion rate. It was found that even if the temperature of the aqueous liquid during the photocatalytic reaction was carried out near room temperature, it could be converted to nitrogen at a very high conversion rate.
本発明の浄化方法においては、上記光触媒反応開始時の上記水性液のｐＨを６〜８に調整することが好ましい。上記光触媒反応開始時の上記水性液のｐＨを６〜８に調整することによって、より高い転化率で上記光触媒反応を進行させることができる。 In the purification method of the present invention, the pH of the aqueous liquid at the start of the photocatalytic reaction is preferably adjusted to 6-8. By adjusting the pH of the aqueous liquid at the start of the photocatalytic reaction to 6 to 8, the photocatalytic reaction can proceed at a higher conversion rate.
上記光触媒反応開始時の上記水性液のｐＨを６〜８に調整する手段としては、任意の適切な手段を採用し得る。好ましい実施形態の一つとして、例えば、本発明の浄化方法が貴金属製造・再生業などの各種産業において排出された廃液中の硝酸性窒素や亜硝酸性窒素の浄化に適用される場合、該貴金属製造・再生業などにおける製造工程において排出されたアンモニアを、ｐＨ調整のために用いる形態が挙げられる。 Any appropriate means can be adopted as means for adjusting the pH of the aqueous liquid at the start of the photocatalytic reaction to 6-8. As one preferred embodiment, for example, when the purification method of the present invention is applied to purification of nitrate nitrogen or nitrite nitrogen in waste liquid discharged in various industries such as precious metal production / regeneration industry, the noble metal The form which uses ammonia discharged | emitted in the manufacturing process in manufacture / regeneration industry etc. for pH adjustment is mentioned.
本発明の浄化方法において、上記亜硝酸性窒素は、水性液中に含まれる硝酸性窒素（ＮＯ３ −）が任意の適切な反応によって亜硝酸性窒素に変換されたものであってもよい。このような反応としては、例えば、硝酸性窒素に対する光触媒反応が挙げられる。 In the purification method of the present invention, the nitrite nitrogen may be one in which nitrate nitrogen (NO 3 − ) contained in the aqueous liquid is converted to nitrite nitrogen by any appropriate reaction. Examples of such a reaction include a photocatalytic reaction with respect to nitrate nitrogen.
上記のような硝酸性窒素に対する光触媒反応の条件としては、任意の適切な光触媒反応の条件を採用し得る。好ましくは、光触媒として、酸化物半導体型光触媒および貴金属系助触媒を用いる。 As conditions for the photocatalytic reaction with respect to nitrate nitrogen as described above, any appropriate conditions for the photocatalytic reaction can be adopted. Preferably, an oxide semiconductor type photocatalyst and a noble metal promoter are used as the photocatalyst.
上記酸化物半導体型光触媒としては、前述したものと同様のものを選択し得る。このような酸化物半導体型光触媒は、１種のみを用いてもよいし、２種以上を併用してもよい。 As the oxide semiconductor photocatalyst, the same one as described above can be selected. Such an oxide semiconductor type photocatalyst may be used alone or in combination of two or more.
上記貴金属系助触媒としては、例えば、金、白金、パラジウム、銀、銅、ロジウムなどが挙げられる。このような貴金属系助触媒は、１種のみを用いてもよいし、２種以上を併用してもよい。 Examples of the noble metal promoter include gold, platinum, palladium, silver, copper, and rhodium. Only 1 type may be used for such a noble metal type | system | group promoter, and 2 or more types may be used together.
本発明の浄化方法は、ラージスケールへの適用が可能であり、高濃度の硝酸性窒素や亜硝酸性窒素を含む水性液への適用が可能であり、装置コストを低減でき、環境負荷が十分に低減され、有害な副生成物の発生を抑制でき、安全性が高いので、好ましくは、水性液が廃液である場合に適用でき、より好ましくは、上記廃液が貴金属製造・再生業において排出される廃液である場合に適用できる。また、本発明の浄化方法で用いる光触媒は、再利用することも可能である。 The purification method of the present invention can be applied to a large scale, can be applied to an aqueous liquid containing a high concentration of nitrate nitrogen or nitrite nitrogen, can reduce the cost of the apparatus, and has a sufficient environmental load. Therefore, it can be applied when the aqueous liquid is a waste liquid, and more preferably, the waste liquid is discharged in the precious metal manufacturing / recycling industry. Applicable to waste liquids. The photocatalyst used in the purification method of the present invention can be reused.
〔参考例１〕：硝酸性窒素から亜硝酸性窒素への転化（Ｐｄ−Ａｇ／ＴｉＯ２光触媒の使用）
パイレックス（登録商標）試験管に、触媒としてＴｉＯ２（Ｄｅｇｕｓｓａ社製、Ｐ２５）：４７．５ｍｇを入れ、さらに、ＮａＮＯ３（関東化学株式会社製）：５００μｍｏｌ（５ｃｍ３）を入れて懸濁させ、シュウ酸ナトリウム：２ｍｍｏｌを加え、助触媒として硫酸パラジウム（関東化学株式会社製）および硫酸銀（関東化学株式会社製）を全触媒重量に対してＰｄが１重量％、Ａｇが４重量％となるように加え、系内をＡｒ雰囲気（バブリング：２０ｍｉｎ）にし、２５℃（２９８Ｋ）にて、４００Ｗ高圧水銀灯の紫外光（＞３００ｎｍ）を照射した。
反応終了後、気相生成物である水素（Ｈ２）、Ｎ２、一酸化窒素（ＮＯ）はガスクロマトグラフ（Ｇ．Ｃ．（ＧＣ−８Ａ：Ｓｈｉｍａｄｚｕ社製、ステンレスカラム：Ｍｏｌｅｃｕｌａｒ Ｓｉｅｖｅ ５Ａ、ＩＮＪ：３１３Ｋ、ＣＯＬ：３２３Ｋ））で定量した。液相のＮＯ２ −、ＮＯ３ −はイオンクロマトグラフ（ＣＯ−２０６０ｐｌｕｓ：日本分光社製）を用いて定量した。また、ＮＨ３および気相の一酸化二窒素（Ｎ２Ｏ）を定量する場合は、イオンクロマトグラフ（ＣＯ−２０６０ｐｌｕｓ、日本分光社製）およびＧ．Ｃ．（ＧＣ−８Ａ：Ｓｈｉｍａｄｚｕ社製、ステンレスカラム：Ｐｏｒａ Ｐａｃｋ−Ｑ、ＩＮＪ：３７３Ｋ、ＣＯＬ：３５８Ｋ）で定量した。
結果を図１に示す。
本参考例１では、図１に示すように、窒素バランス（ＮＢ）を保ちつつ、２４ｈで約９５％のＮＯ３ −が還元された。還元生成物の多くはＮＯ２ −であった。
[Reference Example 1]: Conversion from nitrate nitrogen to nitrite nitrogen (use of Pd—Ag / TiO 2 photocatalyst)
In a Pyrex (registered trademark) test tube, TiO 2 (manufactured by Degussa, P25): 47.5 mg is added as a catalyst, and further NaNO 3 (manufactured by Kanto Chemical Co., Ltd.): 500 μmol (5 cm 3 ) is suspended. Sodium oxalate: 2 mmol was added, and palladium sulfate (manufactured by Kanto Chemical Co., Ltd.) and silver sulfate (manufactured by Kanto Chemical Co., Ltd.) as cocatalysts were 1% by weight of Pd and 4% by weight of Ag with respect to the total catalyst weight. In addition, the inside of the system was placed in an Ar atmosphere (bubbling: 20 min) and irradiated with ultraviolet light (> 300 nm) of a 400 W high-pressure mercury lamp at 25 ° C. (298 K).
After completion of the reaction, gas phase products such as hydrogen (H 2 ), N 2 , and nitric oxide (NO) were gas chromatograph (GC (GC-8A: manufactured by Shimadzu, stainless steel column: Molecular Sieve 5A, INJ). : 313K, COL: 323K)). The liquid phase NO 2 − and NO 3 − were quantified using an ion chromatograph (CO-2060 plus: manufactured by JASCO Corporation). In addition, when NH 3 and gas phase dinitrogen monoxide (N 2 O) are quantified, an ion chromatograph (CO-2060 plus, manufactured by JASCO Corporation) and G.I. C. (GC-8A: manufactured by Shimadzu, stainless steel column: Pora Pack-Q, INJ: 373K, COL: 358K).
The results are shown in FIG.
In Reference Example 1, as shown in FIG. 1, approximately 95% of NO 3 − was reduced in 24 h while maintaining the nitrogen balance (NB). Many reduction product NO 2 - was.
〔参考例２〕：硝酸性窒素から亜硝酸性窒素への転化（Ａｇ／ＴｉＯ２光触媒の使用）
助触媒として硫酸銀（関東化学株式会社製）を全触媒重量に対してＡｇが４重量％となるように加えた以外は、参考例１と同様に行った。
結果を図２に示す。
本参考例２では、図２に示すように、窒素バランス（ＮＢ）を保ちつつ、１２ｈでＮＯ３ −の初期量の約９０％がＮＯ２ −に還元された。これはＡｇの助触媒効果によりＮＯ３ −が選択的にＮＯ２ −へ還元されたものといえる。
[Reference Example 2]: Conversion from nitrate nitrogen to nitrite nitrogen (use of Ag / TiO 2 photocatalyst)
The same procedure as in Reference Example 1 was performed except that silver sulfate (manufactured by Kanto Chemical Co., Inc.) was added as a co-catalyst so that Ag was 4% by weight with respect to the total catalyst weight.
The results are shown in FIG.
In the present reference example 2, as shown in FIG. 2, while maintaining the nitrogen balance (NB), NO 3 at 12h - about 90% of the initial amount of NO 2 - was reduced to. This can be said that NO 3 − was selectively reduced to NO 2 − by the co-catalyst effect of Ag.
〔実施例１〕
パイレックス（登録商標）試験管に、光触媒としてＴｉＯ２（Ｄｅｇｕｓｓａ社製、Ｐ２５）：５０．０ｍｇを入れ、さらに、ＮａＮＯ２（関東化学株式会社製）：５００μｍｏｌ（５ｃｍ３）および（ＮＨ４）２ＳＯ４（関東化学株式会社製）：５００μｍｏｌ（５ｃｍ３）を入れて懸濁させ、系内をＡｒ雰囲気（バブリング：２０ｍｉｎ）にし、２５℃（２９８Ｋ）にて、４００Ｗ高圧水銀灯の紫外光（＞３００ｎｍ）を照射した。光触媒反応開始時の水性液のｐＨは７であった。
反応終了後、気相生成物である水素（Ｈ２）、Ｎ２、一酸化窒素（ＮＯ）はガスクロマトグラフ（Ｇ．Ｃ．（ＧＣ−８Ａ：Ｓｈｉｍａｄｚｕ社製、ステンレスカラム：Ｍｏｌｅｃｕｌａｒ Ｓｉｅｖｅ ５Ａ、ＩＮＪ：３１３Ｋ、ＣＯＬ：３２３Ｋ））で定量した。液相のＮＯ２ −、ＮＯ３ −はイオンクロマトグラフ（ＣＯ−２０６０ｐｌｕｓ：日本分光社製）を用いて定量した。また、ＮＨ３および気相の一酸化二窒素（Ｎ２Ｏ）を定量する場合は、イオンクロマトグラフ（ＣＯ−２０６０ｐｌｕｓ、日本分光社製）およびＧ．Ｃ．（ＧＣ−８Ａ：Ｓｈｉｍａｄｚｕ社製、ステンレスカラム：Ｐｏｒａ Ｐａｃｋ−Ｑ、ＩＮＪ：３７３Ｋ、ＣＯＬ：３５８Ｋ）で定量した。
結果を図３に示す。
本実施例１では、図３に示すように、２５℃（２９８Ｋ）にて、２４ｈ後においてＮＯ２ −とＮＨ４ ＋はほとんど消費され、Ｎ２が生成した。
[Example 1]
In a Pyrex (registered trademark) test tube, TiO 2 (manufactured by Degussa, P25): 50.0 mg was added as a photocatalyst, and NaNO 2 (manufactured by Kanto Chemical Co., Inc.): 500 μmol (5 cm 3 ) and (NH 4 ) 2 SO 4 (manufactured by Kanto Chemical Co., Inc.): 500 μmol (5 cm 3 ) is added and suspended, the inside of the system is placed in an Ar atmosphere (bubbling: 20 min), and ultraviolet light of a 400 W high-pressure mercury lamp at 25 ° C. (298 K) (> (300 nm). The pH of the aqueous liquid at the start of the photocatalytic reaction was 7.
After completion of the reaction, gas phase products such as hydrogen (H 2 ), N 2 , and nitric oxide (NO) were gas chromatograph (GC (GC-8A: manufactured by Shimadzu, stainless steel column: Molecular Sieve 5A, INJ). : 313K, COL: 323K)). The liquid phase NO 2 − and NO 3 − were quantified using an ion chromatograph (CO-2060 plus: manufactured by JASCO Corporation). In addition, when NH 3 and gas phase dinitrogen monoxide (N 2 O) are quantified, an ion chromatograph (CO-2060 plus, manufactured by JASCO Corporation) and G.I. C. (GC-8A: manufactured by Shimadzu, stainless steel column: Pora Pack-Q, INJ: 373K, COL: 358K).
The results are shown in FIG.
In Example 1, as shown in FIG. 3, NO 2 − and NH 4 + were almost consumed after 24 hours at 25 ° C. (298 K), and N 2 was produced.
〔実施例２〕：助触媒の使用
光触媒として、ＴｉＯ２、Ｐｔ／ＴｉＯ２、Ｒｈ／ＴｉＯ２、Ｃｕ／ＴｉＯ２、Ａｕ／ＴｉＯ２、Ｐｄ／ＴｉＯ２、Ａｇ／ＴｉＯ２を用い（助触媒金属はＴｉＯ２の１重量％）、ＮａＮＯ２の量を５０μｍｏｌとし、紫外光（＞３００ｎｍ）を３時間照射した以外は、実施例１と同様に行った。
３時間照射後の結果を表１に示す。
The results after 3 hours of irradiation are shown in Table 1.
〔実施例３〕：光触媒反応開始時の水性液のｐＨ＝４の場合
Ｈ２ＳＯ４（関東化学株式会社製）によって、光触媒反応開始時の水性液のｐＨを４に調整した以外は、実施例１と同様に行った。
結果を図４に示す。
本実施例３では、図４に示すように、Ｎ２の生成量がｐＨ＝７（実施例１）の場合に比べて少なくなった。
Example 3: The case of pH = 4 of the aqueous solution at the start of the photocatalytic reaction H 2 SO 4 (manufactured by Kanto Chemical Co., Inc.), except for adjusting the pH of the aqueous solution at the start of the photocatalytic reaction in 4, performed Performed as in Example 1.
The results are shown in FIG.
In Example 3, as shown in FIG. 4, the amount of N 2 produced was smaller than that in the case of pH = 7 (Example 1).
〔実施例４〕：光触媒反応開始時の水性液のｐＨ＝１０の場合
ＮａＯＨ（関東化学株式会社製）水溶液によって、光触媒反応開始時の水性液のｐＨを１０に調整した以外は、実施例１と同様に行った。
結果を図５に示す。
本実施例４では、図５に示すように、Ｎ２の生成量がｐＨ＝７（実施例１）の場合に比べて少なくなった。
[Example 4]: pH of aqueous liquid at start of photocatalytic reaction = 10 Example 1 except that the pH of the aqueous liquid at the start of the photocatalytic reaction was adjusted to 10 with an aqueous solution of NaOH (manufactured by Kanto Chemical Co., Ltd.). As well as.
The results are shown in FIG.
In Example 4, as shown in FIG. 5, the amount of N 2 produced was smaller than that in the case of pH = 7 (Example 1).
〔実施例５〕：高濃度の場合
ＮａＮＯ２（関東化学株式会社製）および（ＮＨ４）２ＳＯ４（関東化学株式会社製）の濃度をいずれも５ｍｍｏｌとした以外は、実施例１と同様に行った。
結果を図６に示す。
本実施例５では、図６に示すように、基質の濃度が実施例１の１０倍の高濃度の場合であっても、５時間で２０００μｍｏｌ近いＮ２が生成し、その他の副反応も観察されなかった。また、図６のグラフより、反応時間を延ばせば、ＮＯ２ −とＮＨ４ ＋はほとんど消費されてＮ２が生成することが判る。
[Example 5]: Case of high concentration Same as Example 1 except that the concentration of NaNO 2 (manufactured by Kanto Chemical Co., Inc.) and (NH 4 ) 2 SO 4 (manufactured by Kanto Chemical Co., Ltd.) was 5 mmol. Went to.
The results are shown in FIG.
In Example 5, as shown in FIG. 6, even when the concentration of the substrate was 10 times higher than Example 1, N 2 produced nearly 2000 μmol in 5 hours, and other side reactions were also observed. Was not. Further, from the graph of FIG. 6, you wait reaction time, NO 2 - and NH 4 + is seen that almost consumed N 2 is produced.
〔実施例６〕：触媒の再利用
実施例１で使用した光触媒（ＴｉＯ２）を回収し、この回収した光触媒を用いて、再度、実施例１と同様に行った。
結果を図７に示す。
本実施例６では、図７に示すように、反応速度は小さくはなったが、回収した触媒を再利用することが十分に可能であることが判る。
[Example 6]: Reuse of catalyst The photocatalyst (TiO 2 ) used in Example 1 was recovered, and this recovered photocatalyst was used again in the same manner as in Example 1.
The results are shown in FIG.
In Example 6, as shown in FIG. 7, the reaction rate decreased, but it can be seen that the recovered catalyst can be sufficiently reused.
〔比較例１〕
光触媒を用いずに遮光して、２５℃、５０℃、７５℃において、熱化学反応を行った以外は、実施例１と同様に行った。反応時間は５時間であった。
結果を図８に示す。
本比較例１では、図８に示すように、２５℃では反応は進行せず、５０℃、７５℃と温度を上げていくにしたがって、少しずつＮ２が発生した。しかし、７５℃で発生したＮ２はわずかに約１００μｍｏｌ程度であり、また、廃液処理においてこのような温度は危険であり、エネルギー使用量も過大となる。
[Comparative Example 1]
It was carried out in the same manner as in Example 1 except that the thermochemical reaction was carried out at 25 ° C., 50 ° C., and 75 ° C., without using a photocatalyst. The reaction time was 5 hours.
The results are shown in FIG.
In Comparative Example 1, as shown in FIG. 8, the reaction did not proceed at 25 ° C., and N 2 was generated little by little as the temperature was raised to 50 ° C. and 75 ° C. However, N 2 generated at 75 ° C. is only about 100 μmol, and such temperature is dangerous in waste liquid treatment, and the amount of energy used is excessive.
〔比較例２〕
光触媒を用いずに、２５℃において、光化学反応を行った以外は、実施例１と同様に行った。
結果を図９に示す。
本比較例２では、図９に示すように、５時間でＮＯ２ −とＮＨ４ ＋が約２０μｍｏｌずつ反応し、Ｎ２が生成した。しかし、光触媒反応ほどＮ２は生成しなかった。
[Comparative Example 2]
It carried out similarly to Example 1 except having performed photochemical reaction at 25 degreeC, without using a photocatalyst.
The results are shown in FIG.
In this comparative example 2, as shown in FIG. 9, NO 2 − and NH 4 + reacted by about 20 μmol each in 5 hours, and N 2 was produced. However, N 2 was not produced as much as the photocatalytic reaction.
本発明の浄化方法は、ラージスケールへの適用が可能であり、高濃度の硝酸性窒素や亜硝酸性窒素を含む水性液への適用が可能であり、装置コストを低減でき、環境負荷が十分に低減され、有害な副生成物の発生を抑制でき、安全性が高いので、好ましくは、水性液が廃液である場合に適用でき、より好ましくは、上記廃液が貴金属製造・再生業において排出される廃液である場合に適用できる。また、本発明の浄化方法で用いる光触媒は、再利用することも可能である。
The purification method of the present invention can be applied to a large scale, can be applied to an aqueous liquid containing a high concentration of nitrate nitrogen or nitrite nitrogen, can reduce the cost of the apparatus, and has a sufficient environmental load. Therefore, it can be applied when the aqueous liquid is a waste liquid, and more preferably, the waste liquid is discharged in the precious metal manufacturing / recycling industry. Applicable to waste liquids. The photocatalyst used in the purification method of the present invention can be reused.
Claims (10)
光触媒およびアンモニウムイオンの存在下で光触媒反応を行う、
亜硝酸性窒素の浄化方法。 A method for purifying nitrite nitrogen contained in an aqueous liquid,
Performing photocatalytic reaction in the presence of photocatalyst and ammonium ion,
Nitrite nitrogen purification method.
The purification method according to claim 9, wherein the waste liquid is a waste liquid discharged in a precious metal manufacturing / recycling industry.
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| JP2014030787A (en) * | 2012-08-03 | 2014-02-20 | Tanaka Kikinzoku Kogyo Kk | Waste water treatment method |
| CN113042062A (en) * | 2021-03-05 | 2021-06-29 | 景德镇陶瓷大学 | Zinc ferrite-tin oxide composite material, preparation thereof and application thereof in photocatalysis |
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